/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.ranger.authorization.hadoop.utils;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.security.alias.CredentialProvider;
import org.apache.hadoop.security.alias.CredentialProviderFactory;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;

public final class RangerCredentialProvider {
    private static final Logger LOG = LoggerFactory.getLogger(RangerCredentialProvider.class);

    private static final RangerCredentialProvider CRED_PROVIDER = new RangerCredentialProvider();

    RangerCredentialProvider() {
        //
    }

    public static RangerCredentialProvider getInstance() {
        return CRED_PROVIDER;
    }

    public String getCredentialString(String url, String alias) {
        if (url != null && alias != null) {
            List<CredentialProvider> providers = getCredentialProviders(url);

            if (providers != null) {
                for (CredentialProvider provider : providers) {
                    try {
                        CredentialProvider.CredentialEntry credEntry = provider.getCredentialEntry(alias);

                        if (credEntry != null && credEntry.getCredential() != null) {
                            return new String(credEntry.getCredential());
                        }
                    } catch (Exception ie) {
                        LOG.error("Unable to get the Credential Provider from the Configuration", ie);
                    }
                }
            }
        }

        return null;
    }

    List<CredentialProvider> getCredentialProviders(String url) {
        if (url != null) {
            try {
                Configuration conf = new Configuration();

                conf.set(CredentialProviderFactory.CREDENTIAL_PROVIDER_PATH, url);

                return CredentialProviderFactory.getProviders(conf);
            } catch (Exception ie) {
                LOG.error("Unable to get the Credential Provider from the Configuration", ie);
            }
        }

        return null;
    }
}
